“I think it’s a small group of people that have very, very serious problems, I guess,” Mr Trump said.

“If you look at what happened in New Zealand, perhaps that’s the case.

“I don’t know enough about it yet. But it’s certainly a terrible thing.”

Mr Trump was asked about white nationalism and the shooting deaths of 49 people at mosques in Christchurch after he formally vetoed Congress’ resolution to block his declaration of a national emergency at the Mexico border.

A police officer patrols at a cordon near a mosque in central Christchurch (Mark Baker/AP)

His veto, aimed at freeing money to build more miles of a border wall against illegal immigration, is expected to survive any congressional effort to overturn it.

“But I think it’s a horrible event … a horrible, disgraceful thing and a horrible act.”

The man accused of the shootings, whose name was not immediately released, left behind a lengthy document that outlined his motivations.

He proudly stated that he was a 28-year-old Australian white nationalist who hates immigrants and was set off by attacks in Europe that were perpetrated by Muslims.

In a single reference, he mentioned the US president.

“Were/are you a supporter of Donald Trump?” was one of the questions he posed to himself.

His answer: “As a symbol of renewed white identity and common purpose? Sure. As a policy maker and leader? Dear god no.”

The White House immediately denounced the connection.

President Donald Trump speaks in the Oval Office (Evan Vucci/AP)

But the mention from the suspect, who embraced Nazi imagery and voiced support for fascism, nonetheless cast an uncomfortable light on the way that the president has been embraced by some on the far right.

Mr Trump, who as a candidate proposed a ban on all Muslims entering the United States, has drawn criticism as being slow to condemn white supremacy and related violence.

After a 2017 clash between white nationalists and anti-racist protesters in Charlottesville, Virginia, that left one demonstrator dead, Mr Trump said there were “very fine people on both sides” of the confrontation.

He also did not immediately reject the support of David Duke, a former KKK Grand Wizard, during his presidential campaign.

Mr Trump himself telephoned New Zealand prime minister Jacinda Ardern, offering condolences, prayers and any help the US might be able to provide.

New Zealand’s prime minister Jacinda Ardern (AP)

She told reporters she answered: “My message was: to offer sympathy and love to all Muslim communities.”

Mr Trump’s hardline immigration rhetoric and calls to return America to its traditional past have been embraced by many on the conservative fringes, including some who troll online with racist imagery, as well as white supremacists who have looked to engage in violence.

In Florida, Cesar Sayoc, who had decorated his van with Trump propaganda, was accused of posting explosives last autumn to Democratic Party officials and media members, many of whom had been criticised by the president.

The president said Sayoc had been “insane” long before he became a Trump fan.

Last month, a former Coast Guard official was accused of stockpiling weapons in a plot to kill media members and liberal politicians as part of a plan to transform the US into a white ethno-state.

It took more than a week for Mr Trump to respond to the plot, which he deemed “a shame”.

Many experts who track violent extremists have identified white nationalism as a growing threat in the US and abroad.

In January, for example, the New York-based Anti-Defamation League said that domestic extremists killed at least 50 people in the US, in 2018, up from 37 in 2017, and said, “White supremacists were responsible for the great majority of the killings, which is typically the case”.

Some critics have accused US authorities of not dedicating adequate resources to stem a threat of domestic terrorism.

However, The Washington Post reported last week that internal FBI data showed more domestic terror suspects were arrested last year than those allegedly inspired by international terror groups.

This website and associated newspapers adhere to the Independent Press Standards Organisation's Editors' Code of Practice. If you have a complaint about the editorial content which relates to inaccuracy or intrusion, then please contact the editor here. If you are dissatisfied with the response provided you can contact IPSO here